Nanostructured materials and photovoltaic devices including nanostructured materials
Nanostructured materials and photovoltaic devices including nanostructured materials are described. In one embodiment, a nanostructured material includes: (a) a first nano-network formed from a first set of nanoparticles; and (b) a second nano-network coupled to the first nano-network and formed from a second set of nanoparticles. At least one of the first set of nanoparticles and the second set of nanoparticles are formed from an indirect bandgap material. The nanostructured material is configured to absorb light to produce a first type of charge carrier that is transported in the first nano-network and a second type of charge carrier that is transported in the second nano-network. The nanostructured material has an absorption coefficient that is at least 10 3 cm −1 within a range of wavelengths from about 400 nm to about 700 nm.
1. A nanostructured material, comprising:
(a) a first nano-network formed from a plurality of Si quantum dots that are at least one of fused and interconnected; and
(b) a second nano-network coupled to said first nano-network and formed from a plurality of Ge quantum dots that are at least one of fused and interconnected,
said plurality of Si quantum dots having a first peak size that is from about 1 nm to about 20 nm, said plurality of Ge quantum dots having a second peak size that is greater than said first peak size to define a staggered band offset between said first nano-network and said second nano-network,
said nanostructured material being configured to absorb light to produce a first type of charge carrier and a second type of charge carrier, said first type of charge carrier separating into said first nano-network in accordance with said staggered band offset and being-transported in said first nano-network, said second type of charge carrier separating into said second nano-network in accordance with said staggered band offset and being transported in said second nano-network, said nanostructured material having an absorption coefficient that is at least 10 3 cm −1 within a range of wavelengths from about 400 nm to about 700 nm.
2. The nanostructured material of claim 1 , wherein said plurality of Si quantum dots are at least one of fused and interconnected to provide a contiguous conductive path for said first type of charge carrier through at least a portion of said first nano-network.
3. The nanostructured material of claim 2 , wherein said plurality of Ge quantum dots are at least one of fused and interconnected to provide a contiguous conductive path for said second type of charge carrier through at least a portion of said second nano-network.
4. The nanostructured material of claim 1 , wherein said plurality of Si quantum dots have said first peak size that is from about 1 nm to about 10 nm.
5. The nanostructured material of claim 1 , wherein said first type of charge carrier corresponds to electrons, and said second type of charge carrier corresponds to holes.
6. The nanostructured material of claim 1 , wherein said first type of charge carrier and said second type of charge carrier are separated at a boundary between said first nano-network and said second nano-network.
7. The nanostructured material of claim 1 , wherein said absorption coefficient is at least 10 4 cm −1 .
8. The nanostructured material of claim 7 , wherein said absorption coefficient is at least 10 5 cm −1 .
9. The nanostructured material of claim 1 , wherein said nanostructured material has a charge carrier recombination time that is at least 1 ns.
10. The nanostructured material of claim 9 , wherein said charge carrier recombination time is at least 10 ns.
11. The nanostructured material of claim 10 , wherein said charge carrier recombination time is at least 100 ns.
12. The nanostructured material of claim 4 , wherein said plurality of Si quantum dots are interconnected via a first plurality of surface ligands, and said plurality of Ge quantum dots are interconnected via a second plurality of surface ligands.
13. The nanostructured material of claim 12 , wherein said first plurality of surface ligands and said second plurality of surface ligands are selected from charge transfer molecular species, Donor Acceptor molecular species, and conjugated molecular species.